This study was initiated to improve ELISA techniques for serodiagnostic use in parasitic diseases. Sera from patients with well defined acute and chronic schistosomiasis were examined by ELISA using egg, cercarial and adult worm antigens. Sera from acute schistosomiasis patients had higher titers with cercarial than adult worm antigen while patients with chronic schistosomiasis had higher titers with adult worm antigen. We were thus able to distinguish sera from patients with well defined acute and chronic schistosomiasis.